A. Field of the Invention
The present invention relates to an apparatus and method for programming a signal processing circuit of an amplifier, and more particularly, to an amplifier and a portable amplifier programmer capable of being removably connected to the amplifier to read and/or change various parameters of an amplifier signal processing circuit to thereby modify a signal output from the amplifier.
B. Description of the Prior Art
Amplifiers typically have an input port for being connected to an input device such as a musical instrument, a sound system, a public address system, etc. and for receiving audio signals from the input device. The amplifier is also connected to and drives a load or output device such as a loudspeaker. The amplifier includes a signal processing circuit for modifying and amplifying input signals and transmitting the modified signals as output signals to the load.
The signal processing circuits include several resistive elements, capacitive elements, switching elements, operational amplifiers and other suitable devices which are selected to modify an input signal in a desired manner. The various elements of the signal processing circuit define a plurality of sound processing parameters such as a frequency and an amplitude of a cross-over function, relative levels and routing in a mixer, response times, ratios and thresholds in a compressor and frequency, gain and bandwidth in an equalizer.
Thus, when an input signal is transmitted through the various elements of the signal processing circuit, the resultant output signal will have a desired frequency and amplitude in accordance with a signal processing function set in the amplifier.
Users of amplifiers and sound systems often want to modify the signal processing parameters to alter a sound produced by the signals output from the amplifiers. However, it is difficult and time consuming to change the signal processing functions and function parameters in conventional amplifiers for reasons discussed below.
A conventional amplifier 10 is shown in FIG. 3. The amplifier is mounted within an amplifier housing 12 and includes an input port 14 and an output port 16. A load such as a loudspeaker 20 is connected to the output port 16 so that the amplifier 10 drives the loudspeaker 20. A signal processing circuit 30 of the amplifier 10 is located within the amplifier housing 12. The signal processing circuit 30 includes a plurality of signal processing circuit elements which may include a plurality of switches 32, resistors 34 and capacitors 36 and other suitable signal modifying devices (not shown). The signal processing function and function parameters of the amplifier 10 are determined by the plurality of signal processing circuit elements.
The signal processing function and parameters of the amplifier 10 can only be modified by setting one of the switches 32 or removing and/or replacing one or more of the resistors 34 and capacitors 36. However, the amplifier housing 12 must be opened and a signal processing circuit support (not shown) must be removed from the amplifier housing 12 before any of the switches 32, resistors 34 or capacitors 36 can be modified or replaced. After modifying the circuit elements, the signal processing circuit support must be re-inserted into the amplifier housing 12 and the amplifier housing 12 must be closed.
The opening and closing of the amplifier housing 12 and removal of the signal processing circuit support is time consuming and does not allow a user to immediately sound check the results of the modification of the signal processing parameters. Instead, the signal processing circuit support must be reinserted in the amplifier housing 12 to be plugged back into the signal path before the amplifier 10 can be operated. In addition, the modification, removal and/or replacement of the various circuit elements to modify the parameters is a time consuming and difficult process because the signal processing control circuit elements are typically plug-in or solderable components. Also, because anyone is capable of opening the amplifier housing 12 and modifying the signal processing circuit 30, there is no way to prevent an unauthorized modification of the amplifier signal processing parameters.
The conventional amplifier 10 may include a controller 40 for receiving input command signals for modifying the signal processing parameters. The controller 40 can be connected to either manually controllable knobs 50 located on an amplifier control plate (not shown) or to a network 60 comprised of several interconnected amplifiers. If the controller 40 is connected to the knobs 50, any person can make unauthorized modifications to the signal processing parameters by simply turning one of the knobs 50. Also, to repeat the desired settings in a number amplifiers connected in a network, all of the knobs of each of the amplifiers must be individually and manually set to be at the exact same values. If the controller 40 is connected to the network 60, a computer or similar input device must be provided to input control signals through the network 60 to the controller 40 which increases the cost and complexity of the amplifier system.
Also, the presence of the controller 40 in the amplifier 10 introduces noise into the signal path caused by a digital/analog converter required for the controller 40. Further, the amplifier 10 must be provided with a battery backup or other suitable device to provide non-volatility required in digitally controlled systems.